Frequent harassment of my mother by my sister-in-law

I'm writing to seek advise for my mother. My parents live with my elder brother and his wife in my village. Both my elder brother and sister-in-law are primary school teachers and got married in 2017. I'm the younger son and live with my wife in another city where i work. I got married recently in Feb 2022. I find that that the relationship between my sister-in-law and my mother is not very pleasant and there have been frequent heated quarrels between them. The language and behaviour of my sister-in-law during her heat mind is unbearable. Many times she threated us to kill herself and even acted once like she drank poison. It's a kind of her daily routine to make issue out of minor valueless things and targeting my mother to harass and insult her. My mother is 56 and is literally weeping each times she talks to me. As a village person my parents don't want to stay with me in a citylife. Hence, I'm thinking of seeking legal help for my parents.Your advise would save my mother and my family please.